It's not only how for you will drive, but how comfy you want to get to fit them in.
We already had the car packed tight - including 9 machines when I found three more. At least we were only 4 hours from home at that point.
The Davis and MN rode on the floor in front of the passenger seat.
And the Singer sat on the arm rest between us.
So I came home with an even dozen - if we had taken the truck I'd have come home with at least two more treadle machines.